Cooling fan having bent bearing housing for retaining lubricant

ABSTRACT

A cooling fan includes a stator, a base supporting the stator, and a rotor positioned to rotate with respect to the stator. The base includes a bearing housing and a central hole defined in the bearing housing. The rotor includes a hub and a shaft extending from the hub. An end of the shaft is fixed in the hub, and another end of the shaft is extending in the central hole defined in the bearing housing. The bearing housing includes a main cylindrical portion and a protruding portion bent radially inward from a top end of the main portion, and the protruding portion thus serves as a lubricant retaining portion of the bearing housing.

BACKGROUND

1. Technical Field

The present disclosure relates to a cooling fan typically employed in anelectronic device such as a computer, and more particularly to a coolingfan which has a bearing housing with a bent end in order to retainlubricant in the bearing housing.

2. Description of Related Art

With the continuing development of electronics technology,heat-generating electronic components such as CPUs (central processingunits) are generating more and more heat when in operation. In typicaldevices that employ CPUs, the heat requires immediate dissipation.Cooling fans are commonly used in combination with heat sinks forcooling the CPUs.

A typical cooling fan comprises a fan housing having a bearing housingextending upwardly therefrom, a bearing received in the bearing housing,a stator mounted around the bearing housing, and a rotor rotatable withrespect to the stator. The rotor includes a hub and a shaft extendingfrom the hub into the bearing. The bearing housing has an openingdefined at a top end thereof. In assembly of the cooling fan, thebearing is inserted into the bearing housing through the opening.Lubricant is injected into the bearing housing to lubricate the bearingand the shaft. Traditionally, a discrete retaining ring is located atthe top end of the bearing housing to retain the lubricant in thebearing housing, so as to maintain the lubrication of the bearing andthe shaft.

However, rotation of the rotor with respect to the stator during theworking lifetime of the cooling fan is liable to cause the discreteretaining ring to loosen and become deformed. As such, there is a highrisk of the lubricant leaking out of the bearing housing, resulting inincreased friction between the shaft and the bearing. When this happens,the performance of the cooling fan deteriorates, and the lifespan of thecooling fan is shortened.

What is needed, therefore, is an improved cooling fan which can overcomethe above-described shortcomings

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an assembled view of a cooling fan according to an exemplaryembodiment of the present disclosure.

FIG. 2 is essentially an exploded view of the cooling fan of FIG. 1,showing the parts prior to assembly of the cooling fan, including abearing housing partly cut away for clarity.

FIG. 3 is an enlarged view of a circled portion III of FIG. 2.

FIG. 4 is an inverted view of FIG. 2.

FIG. 5 is an abbreviated, cross-sectional view of the cooling fan ofFIG. 1, taken along a line V-V thereof.

FIG. 6 is an enlarged view of a circled portion VI of FIG. 5.

FIG. 7 is an abbreviated, cross-sectional view of a cooling fanaccording to another exemplary embodiment of the present disclosure.

FIG. 8 is an enlarged view of a circled portion VIII of FIG. 7.

DETAILED DESCRIPTION

Exemplary embodiments of a cooling fan in accordance with the presentdisclosure will now be described in detail below and with reference tothe drawings.

FIGS. 1 and 2 show a cooling fan 100 in accordance with an exemplaryembodiment of the disclosure. The cooling fan 100 includes a fan housing10, a bearing assembly 20, a stator 30, and a rotor 50. The rotor 50surrounds the stator 30. The stator 30 and the rotor 50 are received inthe fan housing 10.

The fan housing 10 includes a plate 11, a sidewall 13 extendingvertically and upwardly from a circumferential edge of the plate 11, anda bearing housing 14 extending vertically and upwardly from a center ofthe plate 11.

The plate 11 is flat, and an air inlet 111 is defined in a centralportion of the plate 11. In particular, the air inlet 111 occupies anannular area, and in this embodiment includes three centrosymmetricopenings. Thus the plate 11 includes a base 113 located in a center ofthe air inlet 111, and three connecting sheets 115 extending from aperiphery of the base 113 to connect with portions of the plate 11surrounding the air inlet 111. In this embodiment, the base 113 and theconnecting sheets 115 are integral portions of the plate 11.

The bearing housing 14 is formed on the center of the base 113. In thisembodiment, the bearing housing 14 is integrally formed with the base113. That is, the bearing housing 14 is integrally formed with the plate11, with the bearing housing 14 and the plate 11 being a singlemonolithic body of the same material.

The sidewall 13 includes an arc-shaped surrounding wall 131 surroundinga majority of the rotor 50, a first air-guiding wall 133, and a secondair guiding wall 135. The first air-guiding wall 133 and the secondair-guiding wall 135 extend outwardly from two ends of the surroundingwall 131, respectively. The first air-guiding wall 133 and the secondair-guiding wall 135 are spaced from and parallel to each other, wherebyan air outlet 134 is defined therebetween.

The bearing housing 14 is a central tube and extends from the center ofthe base 113. A central hole 140 vertical to the base 113 is defined inthe bearing housing 14. The bearing housing 14 has an opening defined ata top end of the central hole 140. The central hole 140 has a uniforminner diameter throughout its axial length.

Referring to FIG. 3, the bearing housing 14 includes a main portion 141,and a protruding portion 145 extending upwardly from a top end of themain portion 141 away from the base 113.

The main portion 141 is cylindrical, and extends vertically and upwardlyfrom the center of the base 113. The protruding portion 145 extendsupwardly from the center of the top end of the main portion 141. Thecentral hole 140 extends through the bearing housing 14 from a top endof the protruding portion 145 to a bottom end of the main portion 141connecting the base 113. Inner cylindrical surfaces of the main portion141 and the protruding portion 145 are coplanar. The protruding portion145 is cylindrical (or annular), and an outer diameter thereof issmaller than an outer diameter of the main portion 141.

The bearing assembly 20 includes a bearing 21 and a disk 23. The bearing21 is a sleeve bearing and made from sintered powder such as copperpowder or ceramic powder. A plurality of pores (not shown) is defined inthe bearing 21, and the pores communicate with each other. The bearing21 is received in the central hole 140 of the bearing housing 14 via theopening of the bearing housing 14. The bearing 21 defines an axial hole211 therein. A plurality of channels 213 is defined in the bearing 21.Each channel 213 extending from a center of a top end of the bearing 21radially outward to a peripheral side surface of the bearing 21, andthen down along a peripheral wall of the bearing 21 along a directionparallel to a axis of the bearing 21 to a bottom of the bearing 21.Thus, each channel 213 is L-shaped, and innermost extremities of thechannels 213 at the top end of the bearing 21 communicate with the axialhole 211 of the bearing 21. The channels 213 are radially symmetricallyarranged around the axis of the bearing 21. With the above-describedconfiguration, lubricant at the top of the axial hole 211 is guided to atop portion of the bearing 21, and then returns to a bottom portion ofthe bearing 21 (see below). The disk 23 is made of wear-resistantmaterial, and is located at a bottom end of the central hole 140.

The stator 30 includes an iron core 31, a coil 33, a circuit board 35,and an insulating frame 37. The insulating frame 37 encloses the ironcore 31 therein. The coil 33 is twined around the insulating frame 37.The circuit board 35 is located at a bottom end of the insulating frame37 and electrically connected with the coil 33. The core 31, theinsulating frame 37 and the circuit board 35 are arranged along a commonaxis. As such, a mounting hole 39 is commonly defined through the core31, the insulating frame 37 and the circuit board 35.

Referring to FIG. 4, the rotor 50 includes a hub 51, a shaft 53, amagnetic ring 55, and a plurality of fan blades 57.

The hub 51 includes a circular base plate 511, and a surroundingsidewall 513 extending vertically and upwardly from a circumferentialedge of the base plate 511. A fixing seat 5112 is formed in a center ofthe base plate 511, and the fixing seat 5112 fixes a top end of theshaft 53 therein. A free end of the shaft 53 extends down away from thefixing seat 5112. Preferably, the shaft 53 defines an annular slot 531in a circumferential wall thereof, at a position near a top end of theshaft 53 close to the hub 51.

The magnetic ring 55 is attached to the inner surface of the sidewall513. The fan blades 57 extend radially and outwardly from a periphery ofthe hub 51. An inner diameter of the magnetic ring 55 and an innerdiameter of the hub 51 are both larger than an outer diameter of theiron core 31 and an outer diameter of the insulating frame 37, so thatthe iron core 31 and the insulating frame 37 can be received in themagnetic ring 55 and the hub 51.

The hub 51 encloses the stator 30 and the magnetic ring 55 therein. Themagnetic ring 55 is spaced from the iron core 31 and surrounds theperiphery of the iron core 31.

Referring to FIGS. 5 and 6, when assembling the cooling fan 100, thedisk 23 is inserted into and located at the bottom of the central hole140. The bearing 21 is inserted into the central hole 140. The top endof the bearing 21 is lower than the top end of the protruding portion145, and the bottom end of the bearing 21 abuts against the disk 23.Then, the protruding portion 145 of the bearing housing 14 is bentradially and inwardly to form a lubricant retaining portion 1451. Thelubricant retaining portion 1451 is annular, and defines a through hole1453 in the center thereof. The through hole 1453 communicates with thecentral hole 140, and is aligned with the axial hole 211. An innerdiameter of the through hole 1453 and an inner diameter of the axialhole 211 are both slightly larger than an outer diameter of the shaft53. The free end of the shaft 53 is extended through the through hole1453 of the lubricant retaining portion 1451 and the axial hole 211 ofthe bearing 21 sequentially, to abut against the disk 23. In thisembodiment, the lubricant retaining portion 1451 is formed byhot-melting the protruding portion 145 sufficiently to allow it to bebent.

The lubricant retaining portion 1451 is located between the bottom endof the fixing seat 5112 and the slot 531. An upper surface of thelubricant retaining portion 1451 is near and spaced from the bottom endof the fixing seat 5112, to define a gap 1500 therebetween. The gap 1500helps ensure that the fixing seat 5112 does not interfere with thelubricant retaining portion 1451. The slot 531 is located in the centralhole 140, and completely below the lubricant retaining portion 1451.

An annular narrow space 1600 is defined between the inner edges of thelubricant retaining portion 1451 and a periphery of the shaft 53. Thespace 1600 helps ensure that the shaft 53 rotates within the lubricantretaining portion 1451 without friction. Preferably, as indicated above,the lubricant retaining portion 1451 is located above the slot 531,surrounding the shaft 53. Alternatively, the lubricant retaining portion1451 can extend into the slot 531 (see FIGS. 7 and 8).

Furthermore, the lubricant retaining portion 1451, the bearing 21 andthe shaft 53 cooperatively form a lubricant reservoir 60 above the topportion of the bearing 21. During operation, the rotor 50 is driven torotate by the interaction between an alternating magnetic fieldestablished by the outer cores 31 of the stator 30 and the magnetic ring55 of the rotor 50. Lubricant creeps up along the rotating shaft 53under the influence of the centrifugal force generated by the rotationof the shaft 53, and then escapes to the lubricant reservoir 60 throughin a very small cylindrical clearance 1700 located between the bearing21 and the shaft 53. When the lubricant reaches the top end of thebearing 21, the lubricant escapes into the lubricant reservoir 60. Asindicated above, the lubricant reservoir 60 is cooperatively definedbetween the top end of the bearing 21, the lubricant retaining portion1451 and the shaft 53. The slot 531 of the shaft 53 prevents thelubricant from continuously creeping up along the shaft 53. Since thelubricant reservoir 60 is almost or substantially hermetically sealed bythe retaining portion 1451, the retaining portion 1451 can prevent thelubricant from leaking out of the lubricant reservoir 60. In addition,the lubricant in the lubricant reservoir 60 is guided by the channels213 to return to the bottom portion of the bearing 21, which helpsmaintain the lubrication of the bearing 21 and the shaft 53.

In summary, the lubricant retaining portion 1451 is formed by bendingthe protruding portion 145 of the bearing housing 14 which is formedintegrally with the base 113. Therefore no discrete retaining ring orlocking disk is needed to prevent the lubricant from leaking out of thelubricant reservoir 60, which increases the efficiency of assembling thecooling fan 100 and reduces costs. Furthermore, because the lubricantretaining portion 1451 is located below the fixing seat 5112 with theupper surface of the lubricant retaining portion 1451 being spaced bythe gap 1500 from the fixing seat 5112, the bottom end of the fixingseat 5112 does not interfere with the lubricant retaining portion 1451when the rotor 50 is rotating relative to the bearing 21 at high speed.Moreover, with the narrow space 1600, the shaft 53 does not interferewith the inner edges of the lubricant retaining portion 1451.

It is to be understood, however, that even though numerouscharacteristics and advantages of the embodiments have been set forth inthe foregoing description, together with details of the structures andfunctions of the embodiments, the disclosure is illustrative only, andchanges may be made in detail, especially in matters of shape, size, andarrangement of parts within the principles of the disclosure to the fullextent indicated by the broad general meaning of the terms in which theappended claims are expressed.

What is claimed is:
 1. A cooling fan comprising: a stator; a rotorpositioned to rotate with respect to the stator, the rotor comprising ahub and a shaft extending from the hub, an end of the shaft being fixedin the hub; and a base supporting the stator, the base comprising abearing housing and a central hole defined in the bearing housing,another end of the shaft extending in the central hole of the bearinghousing, wherein the bearing housing comprises a main cylindricalportion and a protruding portion bent radially inward from a top end ofthe main portion, and the protruding portion thus serves as a lubricantretaining portion of the bearing housing.
 2. The cooling fan of claim 1,wherein the lubricant retaining portion is annular, and defines athrough hole in the center thereof.
 3. The cooling fan of claim 1,wherein the shaft defines an annular slot in a circumferential wallthereof, at a position near a top end of the shaft close to the hub. 4.The cooling fan of claim 3, wherein the slot is located in the centralhole, and is completely below the lubricant retaining portion.
 5. Thecooling fan of claim 3, wherein the lubricant retaining portion extendsinto the slot.
 6. The cooling fan of claim 3, wherein an upper surfaceof the lubricant retaining portion is near and spaced from the hub, todefine a gap therebetween.
 7. The cooling fan of claim 1, wherein innercylindrical surfaces of the main portion and the protruding portion arecoplanar before the protruding portion is bent radially inward from thetop end of the main portion.
 8. The cooling fan of claim 7, wherein anouter diameter of the protruding portion is smaller than an outerdiameter of the main portion before the protruding portion is bentradially inward from the top end of the main portion.
 9. The cooling fanof claim 1, wherein the lubricant retaining portion is a hot-meltedportion of the bearing housing.
 10. The cooling fan of claim 1, furthercomprising a bearing received in the bearing housing, wherein the shaftextends through the bearing, a plurality of channels is defined in thebearing, and each channel extends from a center of a top end of thebearing radially outward to a peripheral side surface of the bearing,and then down along a peripheral wall of the bearing along a directionparallel to an axis of the bearing to a bottom of the bearing.
 11. Thecooling fan of claim 10, wherein the bearing defines an axial holetherein, the shaft extends through the axial hole, each channel isL-shaped, innermost extremities of the channels at the top end of thebearing communicate with the axial hole, and the channels are radiallysymmetrically arranged around the axis of the bearing.
 12. The coolingfan of claim 1, further comprising a bearing received in the bearinghousing, wherein the shaft extends through the bearing, and thelubricant retaining portion, the bearing and the shaft cooperativelyform a lubricant reservoir above a top portion of the bearing.
 13. Acooling fan comprising: a base; a bearing housing extending upwardlyfrom the base, the bearing housing defining a central hole therein; anda rotor positioned to rotate with respect to the base and bearinghousing, the rotor comprising a shaft, the shaft extending in thecentral hole of the bearing housing, wherein the shaft defines anannular slot in a circumferential wall thereof, a top end of the bearinghousing is bent radially inward and extends into the annular slot, andthe top end of the bearing housing serves as a lubricant retainingportion substantially sealing a top end of the central hole of thebearing housing.
 14. The cooling fan of claim 13, wherein the bearinghousing includes a main cylindrical portion and the top end extendingfrom the main portion and the top end is bent radially inward from themain portion to serve as the lubricant retaining portion.
 15. Thecooling fan of claim 13, wherein the lubricant retaining portion is ahot-melted portion of the bearing housing.
 16. The cooling fan of claim13, wherein a disk is located at a bottom end of the central hole, andthe disk is made of wear-resistant material.